I. Field
The following description relates generally to wireless communications, and more particularly to protecting pilots from impulsive interference in wireless communication systems.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple mobile devices. Each mobile device may communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in a peer-to-peer or ad hoc wireless network configuration.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. The antennas can relate to both base stations and mobile devices, in one example, allowing bi-directional communication between the devices on the wireless network. In an OFDMA wireless network, mobile devices and/or base stations can transmit data using one or more subcarriers, or tones, of an OFDM symbol. When multiple base stations and mobile devices are present and transmitting data at the same or near the same time intervals and frequency, interference occurs, with respect to receiving the transmissions. To aid in coherently demodulating data in light of unknown channel variations and the aforementioned interference, a reference signal (e.g., a pilot signal), which is typically known to the receiver, is transmitted using a portion of OFDM symbol-subcarrier grid. The pilot signal is typically utilized by the receiver to determine the extent of the noise, interference, and/or translation with respect to a channel used to transmit the data on the OFDM symbols.
In typical wide-area cellular wireless systems, the interference observed persists for a period of time and comes from several interferers with no single interferer being overly dominant. Aspects of the interferers make them appear as white Gaussian noise at a receiver, which can be accounted for by using techniques such as linear filtering. Increasingly deployed ad hoc networks (e.g., hot-spots, home base stations, Femto cells, peer-to-peer, etc.), which facilitate direct device communication without consideration of whether there is a more optimal serving link as in the typical wide-area cellular wireless deployments. Because more optimal serving links can exist without being utilized in the ad hoc deployments, there is a much greater likelihood of dominant interference from the more optimal serving link (or to the more optimal serving link). Moreover, the interference cannot always be averaged as interfering devices may not always have high activity levels. Thus, the interference is impulsive in many cases with respect to timing and degree.